We recently changed our production database disk to SSD.
To clarify, all data paths, caching, tmp, … directory references in the MySQL configuration point to that database disk, now SSD.
The boot disk is still a regular HDD (in GC terms: Standard Persistent Disk). Will the change to a SSD boot disk affect overall performance of our database system?
The system is high read, low write; mostly analytics.
Analyze it this way.
- Every read or write to SSD will be (about) 10 times as fast as to/from HDD.
- Booting involves reading the OS into RAM — perhaps more that a gigabyte of I/O. So boot speed depends on the type of disk.
- Database reads/writes only touch the database directory tree, so their speed is depending on the type of disk it is on.
- There is usually no overlap between boot stuff and database stuff — except that a simple installation throws them both into the same filesystem (hence same HDD or SSD).
/tmpis sometimes put in its own filesystem. This is configurable in the OS. The database can be configured to use
/tmpor some other location. Hence, you may want to make sure MySQL’s
tmpdiris pointing to SSD.
- Most of MySQL’s “caching” is under its own control. So, I don’t see an extra factor here.